In order to see a 95th percentile value in a exact time frame, how can I set the trending time range to specific date times? e.g. from 11/12/2020 11:00:00 to 18/12/2020 11:00:00
As Ruben already mentioned, you cannot achieve this in the trend component just yet.
However, it's already possible to achieve this using an embedded trend component in the Visual Overview. Using the Range option in the ParametersOptions shape data, you are able to configure an exact time window (see help). Note that you can also use session variables to make it more dynamic.